Açıklama
8500 Development of the Microspore Mother Cells – of Lilium candidum – 12 Microscope SlidesLeptotene, the chromosomes appear as fine threads – Zygotene, the homologous chromosomes associate in pairs. The chromosomes appear as strings of beads – Pachytene, complete pairing of the chromosomes – Diplotene, shortening of the chromosomes by contraction. Interchange of chromatin between the maternal and paternal chromosomes (crossing over) – Diakinesis, further contraction of the bivalents, the nuclear membrane disappears – Metaphase and anaphase of the first (heterotypic) division, showing spindle threads. Two haploid sets of chromosomes are separated – Telophase of the first and prophase of the second division – Metaphase and anaphase of the second (homeotypic) division, two mitotic figures are present – Pollen tetrads, four nuclei are formed after the second division, each bearing the haploid number of chromosomes. Formation of cell walls – Uninucleate microspores after separation of daughter cells – Mature two-nucleate pollen grains at the time of shedding. Each pollen grain possesses a tube cell and a generative cell – Mature pollen grains, w.m. to show structure of the cell walls
